1. Field of the Invention
The invention relates to diazotype compositions and their use in diazotype reproductions.
2. Brief Description of the Prior Art
The diazotype reproduction process is well-known to the art and is described in great detail in "Light Sensitive Systems" by Jaromir Kosar, John Wiley & Sons, Inc., N.Y. 1965, and in "Reproduction Coating" by E. Jahoda, 4th Edition, Andrews Paper & Chemical Co., Inc., Port Washington, N.Y.
In general, diazotype reproduction prints are obtained by an imagewise exposure of a light-sensitive diazo material to ultraviolet light followed by development of the exposed diazotype material. There are several different methods available to develop the latent image imposed on the light-sensitive diazo material by the light exposure including ammonia development, amine development, thermal development and moist (liquid) development.
The light-sensitive diazo material generally comprises a light-sensitive diazo composition affixed to a support base such as paper or a synthetic polymeric resin film such as polyethylene terephthalate film, cellulose acetate, or a like base support. The light-sensitive diazo composition may comprise a light-sensitive diazonium salt compound in admixture with diazo enhancing compounds. Upon exposure of the light-sensitive diazonium compound to ultraviolet light through a translucent original having opaque image portions, the unmasked portions of the diazonium salt are decomposed by the ultraviolet radiation whereas the masked portions are left undecomposed. The latent image created by the imagewise exposure may then be developed by the methods described above.
Diazotype materials on paper and film are manufactured in different print colors such as black, blue, yellow, brown and red which use azo dyes generated from one or more diazo compounds and one and more couplers depending on the desired print color shade and printing speed.
Diazotype papers are generally coated with aqueous diazotype preparations while diazotype films are usually sensitized with organic solvent based preparations.
There are only a few applications of yellow diazotypes such as in transparent films for overhead projectors or diazotypes for a very high actinic opacity since the yellow dyes absorb UV light. There is a need, however, for yellow couplers in blackline diazotypes which use a combination of blue-, yellow-, and often together with brown couplers to arrive at a neutral black print color.
Conventional yellow couplers can be classified into two groups with respect to their coupling rates. Classified in descending order, they are:
1. fast coupling compounds: PA0 2. medium to slow coupling compounds:
aceto-acet anilide PA1 bis aceto-acet ethylene diamide PA1 aceto-acet-m-hydroxy anilide PA1 aceto-acet-benzylamide; and PA1 cyanoacetmorpholide PA1 diacyanoacet-triethylene tetramine PA1 m-hydroxy phenyl urea PA1 catechol monohydroxy ethyl ether PA1 o-phenyl phenol PA1 1. reduce the rate of the coupling reaction to an acceptable level which is very much in line with the coupling rate of conventional blue couplers, such as: PA1 2. need no special stabilization for satisfactory shelf life for use in diazotypes; PA1 3. do not tend to migrate from the composition on a support; and PA1 4. product print dyes of better light fastness. PA1 1. Derivatives of 1-diazo-4-amine benzene with or without alkyl, oxylalkyl or halogen substitutions in the benzene ring and with alkyl or dialkyl or acyl or acyl-alkyl substitution on the amino nitrogen or with the amino nitrogen forming a member of a heterocyclic ring with or without a second hetero atom of oxygen or nitrogen. PA1 2. Derivatives of 1-diazo-4-alkylaryl mercapto benzene with or without substitution in the benzene ring. PA1 3. Derivatives of 1-diazo-4-phenyl benzene with and without substitution in the phenyl and in the benzene rings. PA1 4. 2-diazo-1-hydroxy-naphthalene-5-sulfonic acid, and the like. PA1 1. development accelerators; PA1 2. antioxidants to further stabilize diazotype prints against discoloration under daylight exposure; PA1 3. contrast controlling compounds; PA1 4. solubilizers which improve the compatibility of the various components in the sensitizing solution; and PA1 5. shaders to shift colors toward more desirable hues and development.
The first group of yellow couplers can be used only to a very limited degree because they are very difficult to stabilize for an acceptable shelf life of diazotypes, and they couple too fast when they are used to generate complementary azo dyes with the blue dyes obtained from conventional blue couplers in blackline diazotypes. Moreover, they tend to migrate within the coating layer or into the film base or paper upon shelf aging.
The second group of yellow couplers couples too slow when used as the only yellow components to complement conventional blue couplers for the generation of blackline diazotypes, resulting in unsatisfactory and off-shade colors.
It is an objective of this invention to overcome the above shortcomings and to offer a means to produce diazotypes with yellow coupling components that permit the generation of diazotypes with improved shade control, rate of development, and shelf life.